This article is referenced from stackoverflow:

If installed PostgreSQL with homebrew , enter brew uninstall postgresql

If you used the EnterpriseDB installer , follow the following step.

Run the uninstaller on terminal window

sudo /Library/PostgreSQL/9.X/

If installed with Postgres Installer, do:

open /Library/PostgreSQL/9.X/

Remove the PostgreSQL and data folders. The Wizard will notify you that these were not removed.

sudo rm -rf /Library/PostgreSQL

Remove the ini file:

sudo rm /etc/postgres-reg.ini

Remove the PostgreSQL user using System Preferences -> Users & Groups.

  1. Unlock the settings panel by clicking on the padlock and entering your password.
  2. Select the PostgreSQL user and click on the minus button.
  3. Restore your shared memory settings: sudo rm /etc/sysctl.conf